The long-term goal of the proposed preclinical studies is to develop a clinically applicable tolerogenic protocol for use in human islet allotransplantatin in T1D. The central component of our strategy is the delivery of antigens on leukocytes treated with the chemical cross linker 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (ECDI). Autoantigen-coupled splenocytes given IV prevent and treat autoimmunity in mice. In transplant models, ECDI-fixed donor splenocytes given IV on days -7 and +1 - as induce long-term donor-specific tolerance to islet allografts, and when combined with short-term rapamycin (RAPA), also to heart allografts in mice. A first-in-human clinical trial of autologous, peptide-coupled cels in multiple sclerosis (MS) recently established the clinical feasibility of this novel tolerogenic strategy. To test whether the profound tolerogenic efficacy of alloantigen delivery via ECDI-fixed cells (ADEC) will translate to islet transplantation in nonhuman primates (NHP), we will study the following specific aims: AIM #1: To manufacture ADEC products meeting prospectively defined release criteria for evaluation as tolerogens in islet allotransplantation in RM. AIM #2: T determine the efficacy of ADEC in inducing tolerance to islet allografts in RM with low and high memory alloreactivity transiently treated with RAPA, sTNFR, -IL-6R, and LFA3-Ig. AIM #3: To examine the effects of the immunotherapeutic protocol on mechanisms underlying the induction, maintenance, and/or loss of donor-specific tolerance to islet allografts in RM. The innovation of this proposal lies expressly in the preemptive use of potent, yet safe, cellular immunotherapeutics as antigen-specific, negative vaccines. Our protocol targets innate, heterologous, and adaptive direct and indirect pathway immunity (and can be extended to target autoimmunity) and has, despite complete avoidance of generalized T and/or B cell depletion and costimulation blockade, a high potential for inducing durable tolerance to islet allografts in NHP. The proposed studies will provide novel insights into the role of ADEC and concomitant immunotherapy for tolerance induction to islet allografts, a critical step toward clinical translaton of this antigen-specific tolerance strategy.